Create a full matte video or a keyed subject video from chroma-key footage or local neural foreground segmentation.
Where: Flowgen → Add → Video & Motion → AI Edit → Video Matte
Key ideas
- Video Matte is one graph step: Create a full matte video or a keyed subject video from chroma-key footage or local neural foreground segmentation.
- Typed sockets: Inputs: Video / video_in — one source clip.. Outputs: Matte video or Subject video / video_out — depends on Output.; First-frame matte / mask_out — a still mask for inspection or still-image branches.. Settings stay on the node rather than masquerading as extra wires.
- Card and Properties agree: The compact card and selected-node Properties sidebar expose the same persisted controls: Engine: Green screen or This device.; Output: Matte or Keyed subject.; Green screen: key color, spread/similarity, edge softness/smoothness, advanced edge feather, optional backdrop, and color spill for keyed output.; This device: detected source FPS and backdrop for keyed output..
- Execution behavior: Current Green screen and This device engines run locally in the browser. The old Cloud/model engine is intentionally not offered for new nodes and cannot run.
- Cost and privacy boundary: It calls no generation provider and charges no Sparks/Flowies. Processing happens in the open browser, so it cannot execute in a headless/server-only flow and the source must be readable by the page.
- Video Matte card: VideoMatteNode uses the authored shared-card path. Create a matte video or keyed subject with chroma key or on-device segmentation.
- Properties sidebar: Card-owned matte controls; common properties shell
- Opened surfaces: Matte video preview; keyed subject preview
Steps
- Connect a video.
- Choose Green screen for a controlled key color or This device for general foreground separation.
- Choose Matte or Keyed subject.
- Tune engine-specific edge controls, backdrop, and spill removal; source FPS is detected automatically.
- Click Run and confirm long on-device processing if asked.
- Review motion edges across the clip and use mask_out only as a first-frame still.
Inputs
- Video / video_in — one source clip.
Outputs
- Matte video or Subject video / video_out — depends on Output.
- First-frame matte / mask_out — a still mask for inspection or still-image branches.
Controls
- Engine: Green screen or This device.
- Output: Matte or Keyed subject.
- Green screen: key color, spread/similarity, edge softness/smoothness, advanced edge feather, optional backdrop, and color spill for keyed output.
- This device: detected source FPS and backdrop for keyed output.
Important behavior
- Green screen uses local GPU chroma processing.
- This device downloads roughly 94 MB on first use, uses BiRefNet with WebGPU, and can fall back to coarser IS-Net.
- Long local jobs show an estimate and require a second confirmation.
- Old saved Cloud/model mode appears unavailable because that engine is not wired.
MCP authoring
- Create with create_node { type: "videoMatte" }.
- Connect exact handles with connect_nodes when the node has more than one input or output.
- Set the complete control bag described by this article before run_node; set_props shallow-merges node data, so replacing a nested bag requires every value you want to keep.
Video Matte controls and presets
- Add path: Flowgen → Add → Video & Motion → AI Edit → Video Matte.
- Card: VideoMatteNode.
- Properties: Card-owned matte controls; common properties shell.
- Controls: Green screen; This device; Matte; Keyed subject; Key/spread/edge/backdrop/spill; FPS.
- Opened surfaces: Matte video preview; keyed subject preview.
Source FPS and local processing feedback
Green screen and This device now detect and preserve the source frame rate. There is no manual 8/12/24/30 FPS choice to trade temporal resolution. The card shows source-rate detection and measured local progress/remaining-time feedback.
- Output remains Matte or Keyed subject; keyed output uses a chosen backdrop because this video encoder does not preserve transparency.
- Color spill applies to keyed Green screen output, not the grayscale matte.
- This device selects an available local segmentation backend, with refined alpha and temporal handling.
- mask_out is only the first-frame still. Use video_out for time-varying results; Cloud/model remains unavailable.
Tips
- Test the operation on one representative asset before placing it inside a List iteration.
- Keep the untouched source upstream so the operation can be changed or bypassed later.
- Judge edges and color at the intended delivery size as well as at full preview size.
Limitations and important notes
- mask_out represents only the first frame; use video_out for time-varying coverage.
- On-device neural results are coarser without WebGPU and can struggle with motion blur/transparency.
- Cloud/model mode on old saved nodes is unavailable.
Troubleshooting
An old Video Matte node says its engine is unavailable
Switch Engine to Green screen or This device. Cloud/model mode is retained only so saved graphs explain their state.
FAQ
Does this open the full Image Editor?
No. This is a focused Flowgen node. Use Image Editor when you need layers, selections, paint, paths, or several edits in one document.
Can I use it in a List iteration?
Yes. Wire the current row field into the typed input, collect the exact output handle, and test one row before scaling the run.